Selection of pathogen agents in weed biological control: critical issues and peculiarities in relation to arthropod agents

Morin, L.; Evans, K. J.; Sheppard, Andy

doi:10.1111/j.1440-6055.2006.00562.x

Cited by 43 publications

(24 citation statements)

References 117 publications

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“…Recent work in the Australian biological control program for the European blackberry was initiated on the basis of the findings reported here and in the study by Gomez et al (21). The program has focused on the selection and release of additional strains of P. violaceum, potentially possessing a diverse array of alleles associated with virulence and fitness, to provide increased opportunity for the fungus to evolve and adapt to its environment through natural selection (31,32). This strategy was not employed at the commencement of the biological control program in Australia, when only strain F15 was released because it appeared to cause significant disease in common taxa of the R. fruticosus agg.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Dynamics of Introduced Populations of Phragmidium violaceum and Implications for Biological Control of European Blackberry in Australia

Gómez

Evans

Baker

et al. 2008

Appl Environ Microbiol

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Phragmidium violaceum causes leaf rust on the European blackberry (Rubus fruticosus L. aggregate). Multiple strains of this pathogen have been introduced into southern Australia for the biological control of at least 15 taxa of European blackberry, a nonindigenous, invasive plant. In climates conducive to leaf rust, the intensity of disease varies within and among infestations of the genetically variable host. Genetic markers developed from the selective amplification of microsatellite polymorphic loci were used to assess the population genetic structure and reproductive biology of P. violaceum within and among four geographically isolated and diseased infestations of the European blackberry in Victoria, Australia. Despite the potential for long-distance aerial dispersal of urediniospores, there was significant genetic differentiation among all populations, which was not associated with geographic separation. An assessment of multilocus linkage disequilibrium revealed temporal and geographic variation in the occurrence of random mating among the four populations. The presence of sexual spore states and the results of genetic analyses indicated that recombination, and potentially random migration and genetic drift, played an important role in maintaining genotypic variation within populations. Recombination and genetic differentiation in P. violaceum, as well as the potential for metapopulation structure, suggest the need to release additional, genetically diverse strains of the biocontrol agent at numerous sites across the distribution of the Australian blackberry infestation for maximum establishment and persistence.Investigating how pathogen populations evolve can provide a deeper understanding of the factors that contribute to temporal and spatial variation in disease intensity (28). This information is particularly relevant in biological control programs for weeds, when an uncharacterized population or a mixture of strains of a pathogen from the native range of the target weed has been released in the area into which the weed has been introduced. Identifying factors contributing to pathogen evolution can provide insight into how biological control can be improved through the search for and selection and release of prospective biological control agents.There are at least 15 taxa of European blackberry (Rubus fruticosus L. aggregate) in Australia, where this plant is regarded as an invasive species, infesting nearly 9 million hectares of land (17, 41). Taxa of the R. fruticosus agg. are perennial thorny shrubs that are facultatively apomictic and genetically and morphologically variable (34). The distributions of various taxa of the R. fruticosus agg. can be found in a recent taxonomic update on exotic Rubus in Australia (17). Blackberry infestations in Australia may be discontinuous or continuous and of various sizes and shapes. More specifically, infestations can resemble linear corridors (e.g., along roadsides and in riparian zones), discontinuous patches (e.g., in invaded pastures), or continuous, blanket ...

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Section: Discussionmentioning

confidence: 99%

“…The greatest number of release sites, more than 50, were in the state of Victoria (E. Bruzzese, personal communication). Eight other strains were released and strain F15 was rereleased in 2004 at experimental sites in New South Wales and Western Australia (32). The release program has since expanded and is continuing in all southern states of Australia.…”

mentioning

confidence: 99%

Dynamics of Introduced Populations of Phragmidium violaceum and Implications for Biological Control of European Blackberry in Australia

Gómez

Evans

Baker

et al. 2008

Appl Environ Microbiol

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“…Rust fungi are preferentially used over other pathogens in classical biological control of invasive plants principally because of their characteristically high level of specificity (Morin et al 2006). The disadvantage of such high specificity however, is that in situations where the target invasive plant consists of a complex of genotypes with different susceptibilities, the introduction of multiple rust isolates, which together infect the range of target plant genotypes present, is required to adversely impact on the overall plant population (Ellison et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Use of a trap garden to find additional genetically distinct isolates of the rust fungus Phragmidium violaceum to enhance biological control of European blackberry in Australia

Morin

Evans

Jourdan³

et al. 2011

Eur J Plant Pathol

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Biological control agents can be more effective if their populations are genetically diverse, particularly when the target invasive plant comprises a range of genotypes with different susceptibilities and occurs across various microclimates. We report on the use of an efficient approach to find, in the native range, diverse isolates of a rust fungus for biological control. An outdoor trap garden containing various clones of invasive European blackberry (Rubus fruticosus agg.) collected in Australia, each with a different DNA phenotype, was established in France. Within 4 weeks of establishment, the leaf-rust fungus Phragmidium violaceum was recovered from all clones in the garden. Molecular analyses of eight recovered and purified isolates of the fungus from the garden revealed that they were genetically distinct from each other and from isolates already present in Australia. These garden isolates also represented a subset of the population existing in Europe, when compared to isolates collected about 30 years ago. Two pathogenicity phenotypes were observed among the garden isolates in bioassays consisting of representative blackberry clones from Australia, and together the isolates were capable of infecting all clones. Results from host-specificity tests on key non-target plant species closely related to European blackberry concurred with previous findings that the leaf-rust fungus does not pose a threat to commercial blackberry cultivars and Rubus species native to Australia. The release and establishment of the garden isolates in Australia has potential to increase the genetic diversity and evolutionary potential of the leaf-rust fungus for more effective biological control.

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“…It is a regulatory requirement that selected biocontrol candidate agents are host-specific and pose a limited risk towards nontarget plant species (Morin et al 2006). If host specificity can be demonstrated under optimal conditions for disease development in the laboratory/glasshouse, then that strongly indicates that nontarget species will not be affected in the field (Berner and Bruckart 2005).…”

Section: Introductionmentioning

confidence: 99%

Microscopic observations of a compatible host/pathogen interaction between a potential biocontrol agent (Uromyces pencanus) and its target weed (Nassella neesiana)

et al. 2010

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Uromyces pencanus is a prospective biocontrol agent for Nassella neesiana in Australia and New Zealand. The infection process of U. pencanus urediniospores in leaves of its susceptible host N. neesiana was found to be similar to that of most other rust species. A pattern against which to compare nonhost reactions in host range experiments was achieved using a modification of Bruzzese and Hasan's whole leaf clearing and staining technique. The staining of microtome leaf sections provided supplemental information about this pathosystem.

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Selection of pathogen agents in weed biological control: critical issues and peculiarities in relation to arthropod agents

Cited by 43 publications

References 117 publications

Dynamics of Introduced Populations of Phragmidium violaceum and Implications for Biological Control of European Blackberry in Australia

Dynamics of Introduced Populations of Phragmidium violaceum and Implications for Biological Control of European Blackberry in Australia

Use of a trap garden to find additional genetically distinct isolates of the rust fungus Phragmidium violaceum to enhance biological control of European blackberry in Australia

Microscopic observations of a compatible host/pathogen interaction between a potential biocontrol agent (Uromyces pencanus) and its target weed (Nassella neesiana)

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